First thing to rule out would be a loosely connected/shorting safety switch (reverse and seat safety switches both tie in with the Electric PTO) I am uncertain whether your Cub has a set up to bypass the safety switch (about 3-4 years ago they started adding that to some cubs). The reverse safety switch will kill the deck on older (MTD) Cubs WHEN the deck is running and the tractor is put in reverse. If something is amiss with that switch...

Good advise above. If you do confirm that the PTO clutch is faulty- hope that the tractor is within 3 y/o. They have , in the past anyway, had a 3year warantee on the PTO. And they aren't cheap. If not, is this clutch adjustable?

3 years WOULD be about one year more than a battery on a new tractor usually lasts...at least in the Northeast where several months of storage claims batteries regularly...and it IS an electrically engaged PTO....Hmmmmmm. I wonder what the forum's regular posters think?

Probe the connector near the clutch with a 12V test light to determine if power to the clutch remains constant. You can then test the ground side with the test light by probing the ground side of the connector and attaching the alligator clip to 12V. If both remain constant and the clutch lets go it's probably the coil. Be sure to remain in the seat like you normally would while doing this.

No matter what the problem is/was after fixing it I would do as a wise sage here on this forum board suggested and add a relay to handle the clutch coil current. I did so on my Cub LT1050 and I heard a sigh of relief from the switch. Four pin relays are cheap and available at most any auto parts store.

As I recall, I had to jump start mine to get it running after sitting all winter. Then the PTO wouldn't work right even after running and charging the battery for a few minutes. I think the battery fault lamp was on also. I had another battery to swap in from another mower so it was easy diagnosis for me. Thought I'd mention this so you don't run out and buy a new battery needlessly. Although I did have to replace mine at the start of the 4th season.

My wife is 110 pounds and the PTO disengages whenever she bounces on the seat. I weigh 220 and it never does that for me. Any way to adjust or disengage the safety cutoff? I already disconnected the engine shutoff switch under the seat. This mower is 3 years old and it is a POS. I'll never buy anything but John Deere from now on.

My 1872 SG tractor has recently exhibited a similar problem. Sometimes the front PTO will engage and drop right back out, other times it stays engaged, and others it won't engage at all. It also began to have cranking problems at the same time. An odd twist is that if it won't crank right away and I hold the key in the "start" position for a few seconds it will crank and start. I know the start circuit goes through the PTO switch, could this be the cause? The switch bench- tests (continuity) OK in all 3 positions. The relay can be heard if I turn the key on and activate the switch, but it drops out when I turn the key to "start". It's been a great tractor so far.
Thanks

Well I don't know if this will help anyone else, but I found the source of my PTO problem, thanks in part to working in a semi-lit shed instead of outdoors in the sunlight.

It turns out the connector (shell) on the back of the ignition switch was sorta fried and the terminal blade on the switch itself is corroded. I was able to see it arc to ground while working in the shed. Since the engine will continue to run on it's magneto and doesn't need the battery, or associated electrical components to run, any of the accessories from the lights to the ammeter, to the PTO would intermittently fail.

The switch is easy to find, but the connector (unless I buy a complete harness) is another story. I may have to get the switch and try some epoxy on the connector shell

More follow- up
The connector is a Delphi 5P FEMALE BLACK 56 SERIES Automotive. Less than a buck from Mouser Electronics plus about $8 in S&H.

Also on my 1872 adding a relay won't resolve this problem as the current source for the PTO clutch doesn't go through the ignition switch but comes from the engine alternator through the reverse relay.

Well, of course you can add a relay for the purpose of removing the PTO clutch load from the PTO switch.
To do this you will have to provide a new, fused circuit from the same location your OEM ingnition key switch is fed from (usually at the battery cable side of the starter solenoid). Place the fuse near to where the circuit begins.
This new circuit will connect to a standard Bosch type 5 pin relay at terminal #30, this will be power into the relay. Find the "Hot" lead of the PTO clutch pigtail on the CHASSIS SIDE of the 2 wire connector (at clutch under engine). Cut the hot wire about 2" away from the connector so you leave a 2" stub of wire emerging from the connector. Connect a wire from Terminal 87A to the 2" stub of wire.
Connect the cut end of the wire that formerly fed the clutch, to Terminal #85 of the relay. Make a ground lead to connect from relay Terminal #86 to a known good ground point (bolt or screw in metal surface).
The wire that was formerly feeding the PTO clutch is now only serving as the control circuit for the relay, the PTO clutch load is now borne by the relay only.
This augmentation does not defeat any safety switches or interlocks that govern or inhibit operation of the PTO.
The PTO will still be subject to the inhibitions provided by the safety interlocks as the circuit now controlling the relay still travel through all the safety switches it did before.

It will be helpful if you at least post the full model number and serial number obtained from the tractor data plate or data decal. Then we can view the manual online to try and determine what components might be involved in this (carefully review the second post of this old thread to see if any of those conditions may apply.
The correlation between acceleration by using hydro control is likely due to your changing positions slightly on the seat as your body reacts to brace when you increase the ground speed, or the acceleration reaction PLUS whatever action is required for you to move the hydro control.
I will lean (no pun intended) towards it being seat switch related. Would really need to see that wiring schematic for sure.
It might be best if you create a brand new thread of your own to cover this as old threads do not garner as much attention as a brand new one.

LT1045. I did review #2 and thought that was the most likely culprit. I actually disconnected the seat switch about a year ago with no issues. I reconnected it just to make sure and it made no difference (I did verify it was working). The seat switch is not being affected by body movement upon acceleration. I did start a new thread also.
Any assistance is greatly appreciated.

My 2007 LT 1050 gave me trouble with the PTO staying engaged after winter. It would run if I pushed the knob in and out for a few seconds, after doing this the only way to engage it, is to turn the back the key one click and push in the little triangle shaped button and pull the PTO knob out. I'm fixing the wires on the anti reverse linkage that are broke and will try it again

My 1050 LT mows a couple of rounds and then the mower deck stops (PTO?). If I let it set 1/2 hour or so then it will work again for a couple of rounds before stopping again. (Tractor still drives just no mower.)

I've seen PTO assemblies listed at $375. Just spent $400 last fall on starter / wire assembly problems. Worked fine last couple of weeks of last season. Bought new 4 seasons ago at a bigbox.

On my 97 LT1050 I rewired the connections at the safety switch and it solved my problem. But during every couple of cuts I have to wiggle the wires on the safety switch and also the harness on the back of the dash.
PTO's are not as expensive as Ken38 said. this my 2nd one.
the first one was covered under the waranty, but the Cub Cadet dealer and also the manufacturer won't cover the 2nd one. because of the amount of hours on it, they say i'm using it commercialy. I paid just under $200.00 for my PTO
on the internet, and it was the same brand as the dealer wanted $350.00 for If you need the name of the place I can look it up.

My mower worked fine a couple of weeks ago but now the PTO won't stay engaged . The batteryis at least 3-4 years old used contact cleaner to clean all the connections i could get to and it runs longer than it did If I repelace the battery does you think it maight solve the problem

If you look up under the frame where the deck belt is driven by the engine pulley, you will see the electric PTO. Leading into that PTO is a small wire harness. At the other end of those wires (still under the frame) there is an electrical connector. take it apart to effectively disconnect the PTO.
Start the tractor. If the deck still turns, the PTO bearings are seized and need repair/replacing. If not, Look for trouble in the PTO switch on the instrument panel allowing the PTO to be energized full time.

Looks like nobody has talked about this for over a year...but I'd like to revive the issue to see if anyone has had this same problem. I have an '08 Cub Cadet LT 1045. My PTO has just today started disengaging at random times. What is odd to me is that if I drive in reverse, the blades keep going....if I drive slowly in forward they'll keep going too....but if I increase the speed too much (like not even half way) it will shut the PTO off. My mower does have the No Children Around switch on the ignition and so I've been able to work around this problem using that....but I can't help but wonder if there is some kind of sensor on the PTO shutoff that is messed up? Any thoughts would be appreciated.

I will bet that there is an intermittent open in the NORMAL mowing selection circuits of the interlock module that allows the PTO relay to lose its signal long enough to disconnect the PTO.
The open circuit likely mimics an "unsafe action" and thus causes the PTO to be stopped by the interlock module.
I would guess that resetting the mowing selection to NORMAL on the module face will restore PTO operation until it kicks out again.
Selecting the NO CHILDREN AROUND mode likely bypasses some of the interlock circuits and that is why you don't get a glitch when mowing with that selection.
Seems like I recall tomplum making a comment on some other thread about some wiring issue regarding the wires that lead to the reverse sensor switch, but I can't remember when that thread was current.

for a period of time, MTD manual archives did contain a series of free downloadable service manual files for the 1500 series CC tractors. To obtain such, one needs the machine's full technical model number and serial number; entering same to the website for access below. They may still be available.
Within those files are sections addressing the grist of this thread.

So, after I replaced the battery, PTO Switch, the relay AND the PTO Clutch itself and I STILL had the issue, I found a little red wire (hot) that was supposed to be connected to the Reverse Safety Switch at the top of the transmission (under the seat and you need to remove the tire to see it) by way of an "L" shaped female paddle connector. The wire had broken off of the connector and was shorting whenever the bouncing mower made it touch metal.

I suspected the reverse safety switch because I was able to mow by engaging the safety switch override on the ignition switch.

Problem is, the wire is an inch too short to re-connect, so a 2" piece of 14 gauge wire, a wire connector and a new female paddle connector and all appears to be ok (I mowed an acre yesterday and no PTO cut-outs).

Whomever designed the wiring on this mower needs to go to design school. This particular wire actually rides on top of the spring that returns the Forward/Reverse drive pedal back to neutral state. I used electrical tape to suspend the repaired wire so it doesn't touch the spring anymore as I'm SURE that is what caused the issue.